ATPase cycle of Bcs1 AAA-ATPase characterized by high-speed AFM at millisecond time resolution

Abstract

Bcs1 belongs to the superfamily of AAA proteins, ring-shaped homo-oligomeric ATPases associated with numerous cellular activities including protein unfolding and degradation, DNA replication and membrane fusion. Different from many AAA proteins, Bcs1 is a transmembrane protein, a homo-heptamer, that has been demonstrated to act as translocation machinery for the folded Rieske iron-sulfur protein (ISP, a key subunit of the mitochondrial complex-III) across the inner mitochondrial membrane. In general, canonical AAA proteins utilize a hand-over-hand mechanism, where the individual protomer interchange the three different nucleotide states (ATP, ADP, APO) in a sequential manner.